Pneumatically-operated cam-controller.



F. E. CASE.

PNEUMATICALLY OPERATED CAM CONTROLLER.

APPLICATION FILED JUNE 11. 1915.

1,221,676. Patented Apr. 3, 1917.

2 SHEETS-SHEET 1.

OFF

rm/enter: Frank H. Case,

His flttorneg.

F. E. CASE.

PNEUMATICALLY OPERATED CAM CONTROLLER.

APPUCATION FILED JUNE n. 1915.

1,221,676. Patented Apr. 3,1917.

2 SHEETS-SHEET 2.

Inventor: Frank E. Case H 15 Attorney UNITED STATES PATENT OFFICE.

FRANK E. CASE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PNEUMATICALLY-OPERATED CAM-CONTROLLER.

Specification of Letters Patent.

Patented Apr. 3, 1917.

Application filed June 11, 1815. Serial No. 33,496.

To all whom it may concern:

Be it known that I, FRANK E. CASE, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Pneumatically- Operated Cam-Controllers, of which the following is a specification.

This invention relates to the control of electric motors and has for its object the provision of improved means whereby electrlc motors are started, stopped, and generally controlled in a simple, reliable and efficient manner.

While my invention is capable of general application in the motor control field, it is of particular importance in the control of electric railway motors.

It has been the practice in recent years, especially where automatic control is desired, to employ a plurality of electromagnetic switches on contactors for cutting out the starting resistance and making the various connections necessary for starting motors on a series-parallel control system. While this type of control has been very successful in practice, it has not been considered free from objection from the standpoint of complication and weight of control apparatus. One of the main difliculties has been the necessity for interlocking electrical contacts for bringing about the required order of progression of the contactors. One of the objects of my invention is to provide a. system in which the contactors are forced to Operate in a predetermined order by mechanical means.

In one embodiment of my invention, I provide a plurality of unit switches which are normally open, and a cam shaft arranged to close these switches in a mode termined order. The switches are arranged to open quickly and positively when released by the cams on the cam shaft, and may con veniently be provided with magnetic blowouts so that the switches are adapted for opening and closing the motor circuit. For operating the cam shaft, I have found that electropneumatic means are particularly well adapted for the purpose. A supply of compressed air for the air brakes being available, it only remains to properly control the air to cause it to accomplish the desired functions. By the use of compressed air for operating the cam shaft, the switches are caused to close positively and are held in closed position firmly with a minimum expenditure of energy, the weight of the apparatus and the cost being thereby greatly reduced. The electric energy utilized in controlling the compressed air is small compared with the energy required to operate a circuit makin and breaking contactor directly and hol it closed with the proper pressure. By the use of cams for closing the switches, a very heavy spring pressure between the contacting surfaces may be obtained and the opening and closing of the contacts therefore assured.

In one aspect my invention, therefore, comprises a control system for electric motors in which a plurality of unit switches are forced to close against a spring tension by cams which in turn are operated by electropneumatic means under the control of a master controller. In another aspect my invention comprises certain features relating to the operating means, particularly as regards the electro-pneumatic arrangement for quickly closing one of the switches to close the motor circuit on the first step of the master controller, and opening the circuit on this switch when the master controller is returned to off position. Other features of my invention will appear in the course of the following specification in which I have disclosed my invention embodied in a concrete form for purposes of illustration.

In the accompanying drawings illustrating my invention Figure 1 is a diagram of a complete motor control system embodying my improvements; Fig. 2 is a sectional view of the electro-pneumatic means for operatin the unit switches and Fig. 3 is a simpli ed diagram showing only the motor circuits.

I shall first describe a system of control embodying my improvements as a whole, and shall then point out more in detail the specific features of my invention.

Looking first at Fig. 1, it will be noted that I have shown a series-parallel system of motor control in which two motors are employed. It will be understood, however, that my invention is in no sense limited to the articular system employed or to the num er of motors controlled. The armatures of the two motors are designated A and A while the fields which 'are subdivided as hereinafter described are designated F and F. RS designates the reversing switch as a whole, MC indicates the master controller, and LB and LB represent the two line breakers. B represents a potential relay which is denergized so as to return the controller to the oif position upon the failure of power. OR represents an overload relay, D represents a current limit relay or throttle, for causing the advance of the main controller to be under the control of the motor current and E represents a battery for energizing the control circuits.

The main controller, which I have designated M, as shown in Fig. 1, consists of a number of cams arranged upon a shaft so as to close the contactors in a predetermined order. Forming a part of the controller and rotated with the cam shaft are two sets of contacts G and H, the purpose of which will be hereinafter described.

The main controller comprises a number of unit switches one of which is shown at K, (Fig. 2) which switches are operated electropneumatically. Each switch consists of an insulating base upon which is mounted a stationary contact 11, having a magnetic blowout 12, adjacent thereto, and a contact .arm 13 pivoted at 14 and having a contact 15 at its end, cooperating with the stationary contact. The contact arm 13 is normally held in open position by spring 16 as shown in the drawing and is closed by engagement with one of the cam surfaces 17 with a roller 18 on the arm. As before stated, the cams, one of which is shown at 17, are arranged around a shaft 19 and longitudinally thereof, as shown in Fig. 1. The cam surfaces have the proper lengths, as indicated in Fig. 1, to maintain the switches closed for a proper interval. The cam shaft 19 is rotated through the pinion 20 by means of a rack 21 having a piston at each end. These pistons 22 and 23 operate in cylinders 24 and 25 respectively, to which compressed air is admitted through the ports 26 and 27 respectively. The port 26 is normally closed to reservoir and open to atmosphere by the electromagnetically operated valve 28 and is opened by the energization of the magnetizing winding of the valve; while the port 27 is controlled by the normally open electromagnetically operated valve 29. This latter valve is closed when the magnetizing winding is energized. The valve 28, which as above stated is normally closed, connects the cylinder to atmosphere when the winding is deenergized but when the winding is energized, connects the port 26 with the air reservoir so as to admit compressed air to the cylinder 24 so as to move the piston 22 to the left. The valve 29 which is normally open controls the passage from the reservoir to the cylinder so that in the normal position of the valve, with the magnetizing winding deenergized, there will be full reservoir pressure in the cylinder 25. When, therefore, the magnetizing winding of the valve 28 is energized, compressed air will be admitted to cylinder 2i for moving piston 22 to the left, this being the movement which turns the cam shaft in the on direction, that is, to operate the proper switches to bring the motors up to speed. This movement will not take place however, (except as to the first step as hereinafter described) unless the pressure is exhausted from the cylinder 25 by the operation of the valve 29 which closes the connection between the cylinder and the reservoir, and opens the connection between the cylinder and atmosphere. When however, the valve 29 is opened by the deenergization of its winding, full reservoir pressure is admitted to the cylinder 25 so that the pressure on the two pistons 22 and 23 will be balanced. There fore when the magnetizing winding of the valve is energized, and the magnetizing winding of the valve 29 is dei nergized, there will be no movement of the cam shaft, (except on the first step). Moreover, if while the valve 28 is open and the cam shaft is being moved to the on position by the piston 22, the valve 29 should be closed, the movement of the cam shaft will be immediately stopped.

It will be noted that while the piston 22 is fixedly connected to the rack 21, the piston 23 is not so connected with the rack but is yieldingly mounted with respect to the rack. The piston 23 has attached to it a sleeve 30 which fits over the hollowed end of the rack 21, and a spring 31 fits into the hollowed end of the rack, and presses against the inner side of the piston. This arrangement permits movement of the rack to the left so as to compress the spring 31 while the piston 23 remains stationary. In other words, when working pressure is applied to the piston 22, while there is working pressure on the piston 23, the piston 22 will move forward until the spring 31 is fully compressed. This movement causes the cam shaft to move one step to close the motor circuit as will hereinafter appear.

On the top of the cylinder casing is the reverse switch RS comprising a drum P and means for operating the same. The drum is operated pneumatically by means of a double acting piston 32 connected with the cylinder by arm 33. The movement to make the forward connections for the motors is controlled by electromagnetic valve f. while the movement in the direction to connect the motors for reverse operation is controlled by electromagnetic valve r. The construction of this reversing switch forms no part of my invention and need not therefore be described in further detail. The valves 7 and r are of substantially the same character as the valves 28 and 29 and in fact may be of any well known design.

I shall now return to Fig. 1 and describe the operation of the system as a whole. As shown, all the parts are in the positions which they assume when all circuits are deenergized. Assuming now that it is desired to start the motors, the switches 34 and 35 are first closed, switch 34 being closed on its left hand contact. The closure of the switch 35 energizes the potential relay B having contacts 37 and 38 from the trolley T to the winding of the relay, through resistance r to bridging contact 36 on the maincontroller, and thence to ground. If now, the master controller MO is moved to the first position, the reversing switch will be operated by the energization of the electromagnetic valve f in case the reverser should be in the wrong position. As shown, however, the reverser has been left in the forward position so that there is no change with reference to this switch. The line breaker LB now closes, being energized from the battery, through the conductor 39, the contact 40 on the main controller, conductor 41, contact 37 on the potential relay and contact 37' on the circuit breaker, through contacts on the reversing switch and the master controller back to the battery. The line breaker therefore closes but does not close the motor circuit. The line breaker isprovided with two interlocking contacts 42 and 43. The closing of the contact 42 by the closing of the line breaker energizes the magnetizing winding of electromagnetic valve 28, which I shall call the on malgnet, the .circuit being from 1 the battery t rough the interlocking contact 40 through interlocking contact 42, thence through interlocking contacts 38 and 44, back to the battery through the master controller. The energization of the fon magnet while the oif magnet v ve 29 is deenergized, causes the cam sha to move one step by compressing the spring 30 while the piston 23 is held stationary by the pressure against it in a manner previously described. This has the effect of closing the contacts 11 and 15 through the agency of the cam 17. The motor circuit will now be closed from the trolley T through the switch35 and the winding of overload relay OR, the contacts of line breaker LB, through resistance B,

through the contacts on the reversing switch RS, armature A, two sections of field winding F, through the resistance R, R, contacts 11 and 15, resistances .R and B, through the two sections of field windings F and the contacts on the reversing switch, armature A, thence to the throttle or relay D and to ground. The closing of the motor circuit therefore is effected at the contacts 11 and 15 of one of the unit switches. The motors will now run in series with all the resistance in circuit.

\Vhen the master controller is moved to position b, the line breaker LB will be closed, the circuit being from the battery,

through wir 47, interlocking contact 48, interlocking contact 43 on line breaker LB, through the contacts controlled by the throttle magnet D and through one of the contacts G on the main controller, thence to the master controller and back to the battery. Line breaker LB will therefore close and short circuit the resistance R and in closing energize the off magnet of the electromagnetic valve 29, through the contacts 49. The energization of the off magnet causes the cylinder 25 to be exhausted to atmosphere so that the two pistons 23 and 22 move forward causing the cam shaft to move a second step and the cam 50 to close the contacts 51, and short circuit the two sections of resistance R and R Upon the cutting out of the resistances R,R' and R, the. motor current rises so that the throttle D will open its contacts to prevent the controller being moved another step until the current drops to proper value. It will be noted that when the controller starts to take a step, it will complete the step notwithstanding the fact that the throttle contacts through which the off magnet was energized are opened before the completion of the step. This is accomplished by the arrangement of contacts G and H which rotate with the cam shaft. The oil' magnet is energized through one of the contacts G but as soon as the controller has started, circuit is made for the off magnet independently of the throttle contacts through one of the contacts H. This makes a circuit in arallel with the circuit through the throt le contacts, this parallel circuit being through contacts 38 and 44 on the potential relay B r and overload relay OR respectively. The throttle may therefore open, but the movement of the cam shaft will not be interrupted until the circuit is interrupted at contact H and established on the second contact G, which it will be observed, will be when the controller has completed a step to position b. If therefore, the current has not dropped to the proper value when the cam shaft has completed its step, it cannot take another step until the current does drop so as to energize the off magnet through the throttle contacts. When the current does drop to a proper value, the oil' magnet will again be energized to cause the cam shaft to take another step which short circuits the resistance R through cam 50. Again the throttle will prevent further movement of the controller until the current drops to proper value, whereupon another step will be taken by the cam shaft which will short circuit the resistance R. This arrangement by which the main controller will take a complete step although the controller is under the control of the throttle at the beginning of the movement, forms no part of my invention but forms the subject matter of an applieation filed by John F. Tritle, on the 21st day of June 1916, Serial No. 104,721. When the ram shaft moves to the next step (0 on the main controller) in which the fields of the motors are tapped to give increased speed, the progression will stop, by reason of the fact that one of the contacts G, marked 5:2, is offset from the others so as to interrupt the circuit of the off magnet through both sets of contacts G and H. In order to progress further, it is necessary for the master controller to be moved to position e in which the ofi' magnet is energized through the contacts 53, on the master c on troller, and the contact 52 which engages with contact linger 54. The movement of the master controller to the position 0, thercfore. causes the cam shaft to take one step (to position (l) which changes the motor connections from full series with tapped or weakened field. which is the highest speed position in series, to the parallel position. \Vhen this position is reached, the progres sion is stopped by reason of the fact that the contact 54 passes over the contact 52. In order to progress further, it is necessary that the master controller be moved to the position (Z, in which the off magnet will he again energized in the regular way and the cam shaft moved forward step by step in the manner above described under the control of the throttle, until the full parallel position is reached. The main controller will be returned to the olf position at any time by the deenergization of the on magnet controlling the electromagnetic valve 28. This will exhaust the cylinder 24 to atmosphere so that the pressure in cylinder 25 will move the rack 21 to the right and hence turn the controller back to off position. This rleenergization of the on magnet to turn the controller will be accomplished by the deenergization of the potential relay B. If for instance, the power should fail, even for an instant, the potential relay will drop thereby deenergizing the on magnet at the contact 38 of the relay. It will be noted that this potential relay is energized through the contact 36 in the off position of the main controller, but that as soon as the controller moves from off position a holding circuit is made through a resistance r. If therefore, the potential relay should open, it can only be closed if the main controller is in the off position. The revcrser BS is also interlocked with the main controller at contact 40 so that the valve magnets f and r can only be energized in the off position of the controller. The opening of the potential relay causes the opening of the line breaker LB which in turn causes the opening of the line breaker LB and causes another break in the circuit of the on" magnet so that the controller will be returned to off position. It will be understood of course, that at any time when the controller is advancing automatically under the control of the throttle, progression may be stopped by moving back one step on the master controller, which will deenergize the oil magnet and balance the pressure in the two cylinders. For instance, if the master controller is in position b and the main controller is advancing to make the various connections in series, progression may be stopped by bringing the master controller back to the position a. Likewise if the mastercontroller is in position 1! the automatic progression may be stopped by moving the master controller back to the position 0. hen the master controller is moved to the oft position, the on magnet will be deenergized and the main controller returned to off position. Upon the occurrence of an overload, the overload rclay OR will cause the motor circuit to be opened at the line breakers and stop the motors. This overload relay is of the reset type, that is, when it opens it is latched open. The line breakers cannot be closed until the overload relay is reset and then can only be closed by moving the switch 34 on to its right hand contact which will energize the magnet 55 to release the latch and allow the relay to close the operating circuits of the line breakers.

\Vhile I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

\Vhat I claim as new and desire to secure by Letters Patent of the United States is 1. Means for contro ling electric motors comprising a plurality of unit switches each consisting of a stationary contact and a. movable switch arm normally in open position and arranged to open and close the motor circuit, a cam shaft provided with cams for actuating said switch arms in a predetermined order, electropneumatic means for operating the cam shaft in two directions, a master controller and connections whereby the cam shaft is rotated step by step in response to movement of the master controller to successively close the switches.

2. Means for controlling electric motors comprising a plurality of unit switches each consisting of a stationary contact, a movable switch arm normally in open position and arranged to open and close the motor circuit, a cam shaft provided with cams for actuating said switch arms in a predetermined order, electropneumatic means for operating the cam shaft, a master controller, an electrically controlled line switch arranged to be closed in the first position of the master controller and connections whereby the electropneumatic means is operated when the line switch is closed so as to operate the cam shaft one step and close the motor circuit.

3. Means for controlling electric motors comprising a plurality of switches normally in open position and arranged to open and close the motor circuit, a cam shaft provided with cams for actuating said switches in a predetermined order, electropneumatic means for operating the cam shaft, a line switch for controlling the motor circuit, a master controller and connections whereby the line switch is closed on the first ste of the master controller and the cam sha t is rotated one step to close the motor circuit and upon movement of the master controller to the second position, the cam shaft is 1'0- tated step by step to successively close the switches.

4. Means for controlling electric motors comprising a plurality of switches normally in open position and arranged to open and close the motor circuit, a cam shaft provided with cams for actuating said switches in a predetermined order, electromagnetic means for operating the cam shaft, two line switches for controlling the motor circuit, a master controller and connections whereby one line switch is closed on the first ste of the master controller and the cam sha t is rotated one step to close the motor circuit and upon the movement of the master controller to the second position, the second line switch is closed and the cam shaft is then rotated step by step to successively close the switches.

5. Means for controlling electric motors comprising a controller for the motor circuit, pneumatic operating means therefor having a piston and cylinder for each direction of movement, means for simultaneously admitting operating fluid to both cylinders, and means whereby the controller is moved by the movement of one piston with reference to the other while the operating fluid is admitted to the cylinders.

6. Means for controlling electric motors comprising a controller for the motor cirwit and pneumatic operating means therefor comprising an operating member having a piston connected at each end thereof for operating the controller in opposite directions and a yielding connection between one of the pistons and the member to permit the member to be moved with reference to said piston.

7 Means for controlling electric motors comprising a main controller for the motor circuit, pneumatic operating means therefor having a piston and cylinder for each direction of movement, electromagnetic valves for controlling the admission of air to each cylinder, a master controller for the electromagnetic valves and means whereby the controller is moved one step by one piston while there is working pressure in the other cylinder.

8. Means for controlling electric motors comprising a main controller for the motor circuit, pneumatic operatingmeans therefor having two pistons and cylinders one for rotating the controller in each direction throughout its range by a uni-directional movement, an electromagnetic valve for each cylinder, one of which is normally open to admit air to its cylinder and the other normally closed to out 01f the air and exhaust its cylinder, a master controller for the electromagnetic valves, connections whereby the normally closed valve is opened on the first step of the master controller, and means whereby the controller is then rotated while there is working pressure in the other cylinder.

9. Means for controlling electric motors comprising a main controller for the motor circuit, pneumatic operating means therefor having two pistons and cylinders one for operating the controller in each direction throughout its range by a uni-directional movement, and means whereby the controller is rotated upon the admission of air to one cylinder while there is working pressure in the other cylinder.

10. Means for controlling electric motors, comprising a plurality of unit switches normally in open position and arranged to open and close the motor circuit, a ram shaft provided with cams for closing said switches in a predetermined order, pneumatic means for rotating the cam shaft in opposite directions, electropneumatic valves for controlling the pneumatic means, a master controller for the electromagnetic valves, and connections whereby the cam shaft is rotated one step to close the motor circuit when the master controller is moved to the first osition to energize one valve magnet an returned when the magnet is deinergized.

In witness whereof, I have hereunto set my hand this 10th day of J une 1915.

FRANK E. CASE.

It is hereby certified that in Letters Patent No. 1,221,676, granted April 3, 1917,

upon the application of Frank E. Case, of Schenectady, New York, for an improvement in "Pneumaticelly-Operated Cam-Controllers, errors appear in the printed specification requiring correction as follows: Page 1, line 22, for the wordon read or; page 5, line 35 claim 4, for the Word electromagnetic" read electr0 pneumatic; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of May, A. D., 1917.

F. W. H. CLAY,

[SEAL] Acting Commissioner of Patents. 

